Performance Testing of an Inline Electrocoalescer Device With Medium and Heavy Crudes

Abstract

Summary ExxonMobil Upstream Research Company (EMURC) recently completed a subsea technology development and qualification program that included performance testing of an inline electrocoalescer device supplied by FMC Technologies (FMC). This paper will summarize the results from these performance tests. Although heavy oil has been processed onshore successfully for many decades, processing heavy oil in deepwater, subsea, or Arctic fields is extremely challenging. One key challenge is oil/water separation, in which physical separation is constrained by the high viscosity of the crude and the narrow density difference between oil and water. Installing conventional electrostatic coalescers or dehydrators is often not economical or is impractical at remote locations. As part of ExxonMobil's subsea program, several different separation technologies have been investigated and tested that could enable development of these fields. One example of such a technology is an inline electrocoalescer device. An inline electrocoalescer device enhances the coalescence of water droplets dispersed in emulsified oils. This technology has the potential to improve the performance of the downstream oil/water separator considerably. By applying an electrical field to an oil/water mixture, the dispersed water droplets become polarized and reorient themselves in the electrical field. As these water droplets approach one another, attractive forces between the individual water droplets lead to coalescence. Larger water droplets that can be separated faster and more easily in the downstream separation equipment are formed. Such a device can be used to increase the throughput, performance, and reliability of existing oil-processing systems, while reducing the energy consumption and/or use of chemical demulsifiers. In new processing systems, either subsea or topside, deployment of such a device has the potential to significantly reduce the size and weight of the downstream separation equipment, thereby lowering the overall capital expenditure. The results presented in this paper are from performance tests that have been carried out on an inline electrocoalescer device at FMC's testing facilities in the Netherlands, with EMURC's involvement. Extensive testing was executed with both medium and heavy crude oils. The operating temperatures were varied in a range representative for subsea processing applications, where heating of the process fluids is difficult. Thus, the performance of the inline electrocoalescer device was evaluated over a range of oil viscosities. Water-in-oil concentration, flow velocity, upstream shear, and electrical-field strength were also varied to investigate their effects on the performance of the inline electrocoalescer device. The results demonstrate that the unit is able to deliver high preconditioning performance to medium- and heavy-crude-oil emulsions, provided that the appropriate process conditions and electrical settings are used.

A constrained machine learning surrogate model to predict the distribution of water-in-oil emulsions in electrostatic fields

“…Figure 10 illustrates the size distribution of droplets in two scenarios: (i) without the utilization of an electric field (IEC switched off) and (ii) with an electric field (IEC switched on), comparing the predictions of the surrogate model to the experimental data 12 . The distribution is represented by plotting the cumulative volume fraction of droplets against their diameter at the electrostatic coalescer outlet.…”

“…Kooti et al utilized a population balance modelling approach to simulate the dynamic and complex processes of coalescence and breakage of water-in-oil emulsions in inline electrostatic coalescers 11 . IEC is a pipe-based device equipped with a series of insulated active and grounded electrodes, exposed to an AC electric field 12 (Fig. 1 ).…”

“…For a more in-depth mathematical background, refer to Kooti et al in the cited literature 11 .

Figure 1 A schematic representation of an inline electrostatic coalescer device 10 , 12 .

Figure 2 Temporal changes in the number density distribution of water droplets ( ) with different diameters per unit volume at the outlet of IEC 11 .

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“…Recent advancements in electro-coalescence technology, such as inline electrostatic coalescers (IEC), have improved water separation efficiency 10 , 11 . These devices subject the water/oil mixture to an AC electric field, magnifying droplet sizes and enhancing coalescence rates in the pipeline to facilitate the water separation downstream reducing the reliance on demulsifying chemicals and promoting an environmentally friendly approach 12 . IECs are particularly crucial for increasing the efficiency of dehydration in heavy oil processing and offshore operations, as they effectively counteract the emulsion stabilizing effects of surface-active compounds in heavy crude oil, such as asphaltene and resin while providing a compact design, light weight, and superior performance particularly beneficial in limited-space offshore units.…”

“…We employed permutation and Shapley additive explanations (SHAP) methods to evaluate the influence of the input parameters on the modelling output. The efficiency of the constrained XGBoost model was assessed by comparing its predictions to a standard XGBoost model as well as experimental data 12 , 22 and the outcomes of the phenomenology-based mathematical model 11 .…”